A value of Tense Feature assigned to the designated element in the clause when the meaning selected for the clause is that intended to locate the event spoken about as anterior, simultaneous, or posterior to the deictic centre of the utterance, and additionally the reference point from which this event is viewed is separated and moved away from the event time. This alters the viewing of the temporal location of the event even though the event's actual location with respect to the deictic centre remains the same. 'Perfect' temporal relations contrast with 'simple' temporal relations in which the reference point coincides with the location of the event spoken about. Modelling of this distinction originates from [Reichenbach 1947].

There are two types of 'perfect' context which may lead to separate tense values:

(1) The first type occurs when the reference point is moved away from the event time and instead located after the event time. A common example occurs with an anterior temporal relationship, when the reference point is moved from the event time to the moment of speech. The event time is anterior to the moment of speech, but it is viewed against a stretch of time which began at the event and continues up to the moment of speech --- e.g. the English I have read this book, I have seen John --- hence the interpretation that the event has an effect or is in
some way still relevant at the moment of speech. [Note that in some languages (e.g. English) this tense meaning is labelled as (one of the uses of the) Present Perfect, in others (e.g. Polish) this meaning may be collapsed with the 'simple' anterior meaning and labelled simply as
Past.] The interpretation of this type of the perfect often includes at least two related but distinguishable uses: the resultative perfect (Someone has stolen my purse) and the experiential perfect (I have read this book before) [Dahl and Velupillai 2005,271].

(2) The second type occurs when the reference point is moved away from the event time and instead located before the event time. A common example occurs with a simultaneous temporal relationship, when the reference point is moved from the event time and located before the moment of speech. The event time is still simultaneous with the moment of speech, but it is viewed against a stretch of time which began at the reference point and continues up to the moment of speech --- e.g. the English I have lived here [for ten years] --- hence the interpretation that the event which began in the past extends up to the moment of speech. [Note that in some languages (e.g. English) this tense meaning is labelled as (one of the uses of the) Present Perfect, in others (e.g. Polish) this meaning may be collapsed with the 'simple' simultaneous meaning and labelled simply as Present.] The interpretation of this type of the perfect is often referred to as the universal perfect or perfect of persistent situation.

Typically, for a tense value to be labelled as Perfect Tense, the tense meaning has to minimally express the meaning resulting from the separation of the reference point from the event time, although it may additionally express other temporal, aspectual, or modal meanings.